Sand consolidation composition

ABSTRACT

Method of and composition for the treatment of unconsolidated sandy formations to stabilize the formation comprising injecting a treating composition consisting essentially of, on a volume basis, 10 to 25% of furfuryl alcohol, 1-4% of a nonionic dispersing surfactant, 1-4% of water, 0.5-1.5% of a silane coupling agent, 1-5% of a catalyst, 5-15% of a low in aromatics petroleum distillate fraction and 47 to 76% of a high in aromatics petroleum fraction, into said sand formation, effecting polymerization of said furfuryl alcohol, and forming a fluid permeable consolidated sand in said formation.

This is a division, of application Ser. No. 753,760, filed Dec. 23,1976.

FIELD OF THE INVENTION

The present invention relates to the treatment of permeable undergroundformations. More particularly, the present invention relates to a methodof treating permeable underground oil and/or gas containing formationsto stabilize the sandy portion thereof and to a treating compositionuseful in the stabilization of incompetent sand containing undergroundformations.

The recovery of fluids such as gas and/or oil from undergroundformations has been troublesome in areas wherein the undergroundformation is composed of one or more incompetent sand containing layersor zones. The sand particles in the incompetent zone and/or layer tendto move or migrate to the well bore during recovery of the formationfluids from the particular zone and/or layer and frequently the movingsand particles block the passageways leading to the well bore. Pluggingor materially impairing the flow of the formation fluids toward theborehole results in a loss of these fluids to the producer or sodecreases the rate of oil recovery from the well as to cause the well tobe shutdown because it is economically unattractive to continue toproduce therefrom. An additional adverse factor resulting from themovement of the sand particles toward the well bore is that they areoften carried along with the formation fluids to the well bore andpassed through the pipes, pumps, etc. being used to recover theformation fluids to the surface with resulting damage to the movingparts thereof as the sand particles are very abrasive.

DESCRIPTION OF THE PRIOR ART

Many attempts have been made heretofore to prevent or decrease the flowof undesirable sand particles from the formation into the productiontubing and associated equipment, such as by the placement of sandscreens, filters, liners and so forth. These prior attempts have beenunsuccessful for a number of reasons among which is that thesemechanical devices fail to prevent completely the flow of the formationparticles into the production equipment. In addition, these devicesinterfere with various types of completion and workover operations. Inrecent years, the industry has attempted to avoid the difficultiesencountered in the use of mechanical devices by employing variouschemical compositions to effect consolidation of the undergroundincompetent formations. These methods have generally consisted ofinjecting into the underground formation polymerizable resinousmaterials which when subsequently polymerized form permeable barriers inthe formation to prevent to the sand particles from movementtherethrough. However, this technique of sand consolidation has not metwith widespread acceptance because of the inherent difficulties ofeffecting polymerization of the resinous materials in the formation to adegree sufficient to consolidate these underground formations and yetpermitting the unobstructed flow of the desirable formation fluidstherethrough. Further, the cost associated with these resin coatingmethods has been relatively high in comparison with the prior mechanicalmethods and the time required for resin polymerization is often ratherlengthy at low temperatures.

SUMMARY OF THE INVENTION

By the method of the present invention one is able to treat effectivelythe underground formation to be stabilized in a rapid and efficientmanner while minimizing the disadvantage of these prior art methods,both mechanical and chemical.

One object of the present invention is to provide an improved method oftreating underground sand containing formations to stabilize theincompetent formation. An additional object is to provide a fluidpermeable consolidated formation sand between the loose formation sandand the well bore so as to prevent or to minimize the flow ofunconsolidated sand particles therethrough while maximizing the flow ofdesired fluids and particularly petroleum hydrocarbons therethrough. Astill further object is to provide a novel treating composition for usein stabilizing incompetent sand formations and to a method of placingsame.

How these and other objects of the invention are accomplished willbecome apparent with reference to the accompanying disclosure. In atleast one embodiment of the method of this invention at least one of theforegoing objects will be obtained.

It has now been discovered that an improved method of treating anincompetent sand containing underground formation comprises introducinginto said formation a particular treating composition consistingessentially of, on a volume basis, from about 10 to 25% of furfurylalcohol, from about 1 to 4% of a surfactant, from about 1 to 4% ofwater, from about 0.5 to 1.5% of a silane coupling agent, from about 1to 5% of a catalyst, from about 5 tp 15% by volume of a low in aromaticspetroleum distilled fraction and from about 47 to 76% of a high inaromatics petroleum fraction, effecting polymerization of said alcoholin the formation sand to be consolidated. The resultant consolidatedsand serves to prevent or to reduce materially the flow of theunconsolidated sandy particles therethrough while permitting the flow ofdesirable formation fluids at a substantially unimpaired rate.

In carrying out the method of the present invention it is necessary tofirst remove any water present in the tubing and casing around the areato be treated since excess water might cause the treating composition toseparate. This may normally be carried out by use of a spacer of dieseloil or other hydrocarbon. Thereafter the treating composition is pumpeddown the well bore under sufficient pressure to force the compositioninto the unconsolidated formation adjacent to or in reasonable proximityto the well bore. When the composition is suitably placed in theformation the well is shut in for the time required to effectpolymerization of the alcohol component by the catalyst component underthe elevated temperature of the formation.

On polymerization the furfuryl alcohol component of the composition setsup and hardens and there is formed a fluid permeable consolidated sandthat prevents or decreases the movement of sand particles therethroughinto the well bore. After the alcohol polymerizes and hardens, the wellcan be equipped for production. The formation fluids can be recoveredtherefrom by permitting these fluids to pass through the resultingformed consolidated sand in the formation into the well bore andrecovered therefrom without the formation fluids being contaminated withthe presence therein of unconsolidated sand particles.

The method of the present invention is particularly adaptable for use inany type of well completion but is generally used in a well whereincasing has been set and which has perforations therein at the desiredintervals behind which the unconsolidated formation sands are located.Packers can be initially set above and below the perforated intervals toprevent the treating composition from passing into the non-isolatedportions of the well and also to permit build-up of sufficient pressureson the said composition to force same through the performations and intothe formation without plugging up the well bore. After the treatingcomposition has been forced through the casing performations and intothe unconsolidated dry sand formation the well is usually closed in fora suitable period of time to permit the catalyzed alcohol to set andharden.

The treating composition useful in the method of the present inventionmust meet certain specific requirements. The concentration of furfurylalcohol present in the treating composition can vary from about 10 toabout 25% by volume, with excellent results being obtained atconcentrations of between 15 and 20%, and particularly at about 18-19%for the most effective results. Amounts above about 25% of the alcoholare to be avoided because the solution is unstable and may separate.Alcohol concentrations below about 10% are not desirable because theconsolidation is apt to be weak in compressive strength.

One of the essential components of the treating composition is anonionic surface active dispersing agent which is used in an amount offrom about 1 to about 4% by volume, and preferably about 2-3% by volume.This component serves to disperse the water soluble components of thecomposition in the oil components. Suitable surface active dispersingagents include Pluronic L-64, a polyoxypropylene-polyoxyethylenecondensate obtained by the condensation of propylene oxide withpropylene glycol and the addition of ethylene oxide to both ends of thepolyoxypropylene base. This material has a hydrophilic lipophilicbalance of 15.0 and an average molecular weight of about 2900.

Another suitable oil soluble surface active agent is the nonionicsurfactant known by the trade name Hyflo, and described more fully inU.S. Pat. No. 2,946,747, as an oil soluble amine salt of an alkylatedaromatic sulfonic acid and a polyether synergizing component capable ofreducing the surface tension of water by at least 25 dynes/cm² andhaving an average M.W. of at least 1200 attributable to oxyalkylenegroups having 2 to 4 carbon atoms, the relative proportion of the saltbeing 3 to 20 times by weight of the synergizing component.

The nonionic dispersing surfactant known by the trade name PolycomplexQ, can also be used.

Another essential component of the composition is from about 1 to 4% byvolume of water, and preferably about 2 to 3%. This component reactswith the acid chloride catalyst component to form hydrochloric acid,which in turn polymerizes the alcohol component.

Another component of the composition is the silane coupling agent, whichis used to impart additional strength to the consolidated sandformation. It functions to improve surface adhesion of the alcohol tothe sand grains, thus improving the compressive strength thereof. Whileany of the known silane coupling or bonding agents can be used, it ispreferred to employ a particular silane, namely gamma-glycidoxypropul--trimethoxysilane in the composition. A suitable quantity thereof mayvary from about 0.5 to about 1.5% by volume, preferably from about 0.7to 1.3%.

A suitable catalyst component of the composition must function to effectpolymerization of the furfuryl alcohol after placement in the sandformation being consolidated.

Representative catalysts such as organic acid halides likemethanesulfonyl chloride, benzoyl chloride and benzenesulfonyl chloridecan be used. The expecially preferred catalysts are benzoyl chloride andbenzenesulfonyl chloride. Any of these catalysts, alone or in admixtureare satisfactory, and can be used at concentrations of from about 1 to5% by volume, preferably 1.5 to 3.5%, for most satisfactory results.

The solvent components should be of the type to effect solubilization ordispersion of the furfuryl alcohol and remaining components therein.

It has been found necessary to employ a mixture of solvents for thecomposition of the present invention.

One solvent component is a high in aromatics, (80% or more), petroleumfraction obtained as naphthalene petroleum fraction from a toppedcatalytic bottoms fraction having an IBP of about 350° F. and an EP ofabout 750° F., an API Gravity of about 20° C., and a Flash Point ofabove about 150° F. (COC).

This high in aromatics fraction is used in an amount of from about 47 to76% by volume, preferably from about 55 to about 75%.

The other solvent component can be a low in aromatics (20% or less)petroleum distillate fraction such as a kerosene fraction or a dieseloil fraction having a cetane no. of at least 45 and a boiling range offrom about 310° F. to about 540° F., an API Gravity of 41° to 47° C. anda Flash Point of at least 120° F., (COC).

This petroleum distillate fraction is employed at a concentration offrom about 5 to 15% by volume, preferably from about 8 to 12%.

It is to be noted that at ambient temperatures the treating compositionis relatively stable (the furfuryl alcohol component will not polymerizeto an objectionable degree even in the presence of the catalystcomponent) for a period of time sufficient to permit preparation of thecomposition and its placement in the formation. On placement in theformation, the formation temperature along with the catalyst componentis sufficient to effect polymerization of the furfuryl alcohol componentwith resultant consolidation of the formation. Typical formationtemperatures effective to permit polymerization within about 24 hoursare in the range of from about 100° F. up to 300° F., usually from about100° F. to about 250° F.

In the practice of this invention the formation to be consolidated canbe essentially waterfree or dry. Drying of a water wet formation can beaccomplished in a known manner such as by displacement with an organicsolvent for water such as acetone, 2-propanol, dioxane and the like. Anessential characteristic of this organic solvent is that it benon-reactive with the catalyst component. While the treating compositioncan be used in wet sands there is some loss in compressive strength.

The treating composition of the present invention is employed in thefollowing manner.

After drying the formation, if necessary, the treating composition isintroduced into the bore hole and then displaced into the formation tobe consolidated. Suitable displacement fluids for the treating solutioninclude the solvent component of the solution itself or other similarproducts.

Rates of injection of the treating solution may vary from about one toabout three gallons per minute per perforation. An injection rate offrom about 1.5 to 2.5 gallons is preferred.

Following is a description by way of example of the method of thepresent invention.

EXAMPLE 1

A one inch in diameter by 6 inches long glass tube was filled with a dryOklahoma #1 sand having a known permeability of about 13 darcies.

The sand was packed in the tube dry by vibration. The packed sand wastreated with 40 ml. of the treating solution of the invention. Thetreating solution was composed of 80 ml. of furfuryl alcohol, 8 ml. ofnonionic dispersing agent, Polycomplex Q, 8 ml. of water, 4 ml. ofgammaglycidoxypropyl -- trimethoxysilane, 10 ml. of benzene sulfonylchloride catalyst, 40 ml. of a essentially low in aromatics petroleumsolvent having an API Gravity of 41°-47° C., a Flash Point (COC) of 120°F. minimum, and a boiling range of 310°-540° F., and 280 ml. of a highin aromatics petroleum distillate solvent having an API Gravity of 20°C., max., a boiling point range of 350°-750° F., and a Flash Point (COC)of a minimum of 150° F., and being a naphthalene petroleum fraction of atopped catalytic reformate bottoms cut. The treated sand packed tube washeated at 80° C. overnight.

Thereafter the consolidated sand was removed from the tube andcompressive strength and permeability measurements were obtained. Theconsolidated sand showed compressive strengths of 500-2300 psi. Itsstability to flowing oil, brine and mixtures in three separate tests,conducted at 200° F., flow rates of 200 ml/min., through 1 in. diameterby 1 in. long samples of consolidated sands by the compositions of theinvention was found to be comparable to that of commercial sandconsolidation compositions.

EXAMPLES 2-3

Similar results to those of Example 1 were obtained using thedispersants Hyflo and Pluronic L-64 in place of Polycomplex Q.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof and therefore only such limitations should be imposed asare indicated in the appended claims.

I claim:
 1. A treating composition for use in forming a fluid permeablebarrier film in a sand containing, unconsolidated oil producingformation which consists essentially of, on a volume basis, 10 to 25% offurfuryl alcohol, 1 to 4% of a nonionic dispersing surfactant, 1 to 4%of water, 0.5 to 1.5% of a silane bonding agent, 1 to 5% of apolymerization catalyst for said furfuryl alcohol, 5 to 15% of alow-in-aromatics (about 20% maximum) petroleum distillate fraction, andfrom about 47 to about 76% of a high-in-aromatics (above about 80%)petroleum fraction.
 2. Composition as claimed in claim 1 wherein saidfurfuryl alcohol concentration is from 15 to 20%.
 3. Composition asclaimed in claim 1 wherein said alcohol concentratiion is from 18-19%.4. Composition as claimed in claim 1 wherein said nonionic dispersingsurfactant is obtained by the condensation of propylene oxide withpropylene glycol and the addition to both ends of the polyoxpropylenebase of ethylene oxide, and wherein the Hydrophilic - Lipophilic Balanceis 15.0 and the M.W. is about 2900, and is present in an amount of from2 to 3%.
 5. Composition as claimed in claim 1 wherein the waterconcentration is 2-3%.
 6. Composition as claimed in claim 1 wherein saidsilane bonding agent is present in an amount of from 0.7 to 1.3%. 7.Composition as claimed in claim 1 wherein said silane bonding agent isgamma glycidoxypropyl - trimethoxysilane.
 8. Composition as claimed inclaim 1 wherein said furfuryl alcohol polymerization catalyst is presentin an amount of from about 1.5 to 3.5%.
 9. Composition as claimed inclaim 1 wherein said low-in-aromatics petroleum distillate fraction ispresent in an amount of from about 8 to 12%.
 10. Composition as claimedin claim 1 wherein said high-in-aromatics petroleum fraction is presentin an amount of from 55 to 75%.